The present invention relates to a method of compacting radioactive metal wastes from nuclear reactors, such as fuel claddings of zircaloy and used metal materials of zirconium or zircaloy occluding tritium.
Use of a hot isostatic press (HIP) or hot press (HP) has already been proposed in compacting radioactive metal wastes such as zircaloy cladding hulls. The method employing the HIP is practiced by enclosing zircaloy cladding hulls in an HIP treating capsule made of stainless steel or the like and evacuated to a vacuum, placing the capsule into an HIP treating container, and subjecting the capsule to a high isostatic pressure (e.g., of 100 kgf/cm.sup.2) at a high temperature (e.g., 1000.degree. C.) using, for example, argon gas (Ar gas) as a pressure medium to compact the zircaloy cladding hulls into a solid metal block of high density.
The zircaloy cladding hulls to be treated by the conventional compacting method with the use of the HIP have occluded therein tritium .sup.3 H), radioactive isotope of hydrogen, in an amount of 60% of the amount thereof produced in the reactor. At a high temperature, the tritium is released from the hulls and then penetrates through the capsule, contaminating the pressure medium, i.e., Ar gas, and the HIP treating container. Consequently, the conventional method requires aftertreatments of a large quantity of Ar gas and the container to remove the contaminant tritium, necessitating much labor for these procedures.
The same problem will be encountered with the compacting method utilizing the HP.